BOOSTXL-DRV8305EVM: Current scaling

Ananthkumar Selvaraj

Part Number: BOOSTXL-DRV8305EVM
Other Parts Discussed in Thread: DRV8305, DRV8323

I am using LauncpadXL 28379D + DRV8305EVM.

DRV8305, Gain is 10 V/V, Rshunt resistance is 0.007 ohm (DRV8305EVM) .

max input current, +19.3 A = 3 V from DRV 8305

Input current, 0A = 1.65 V from DRV 8305

What is the max negative current read by DRV8305?

What is the voltage output of DRV 8305 at its max negative current?

I need this information for calibrating the current. I am little confused over here. I want to clarify myself. Thanks.

0 Adam Sidelsky over 5 years ago

Ananthkumar,

Please see the example in the DRV8323 datasheet at section 9.2.1.2.4.

Regards,

-Adam

0 Ananthkumar Selvaraj over 5 years ago in reply to Adam Sidelsky

Hi Adam,

This document gives me good insight.

But I want to confirm my understanding. Sorry for ringing around same question.

LaunchPad28379D + Boost XL-DRV8305EVM

Vref=3.3 V

Vswing=0.3 V (from previous forums)

Gain=10 V/V

Offset voltage is 1.65 V.

Bi-directional current measurement,

Max positive measurable current = +19.3 A, (1.65 V to 3 V)

Max negative measurable current = -19.3 A, (0.3V to 1.65 V)

Measurable ADC input voltage 2.7 V (0.3V to 3 V) corresponds to 19.3*2 A.

ADC count for 3 V is 4095

ADC count for 2.7 V is 3685.5 (measurable range) and this corresponds to 19.3 A * 2.

So, ADC counts per A is 3685.5/(19.3*2) = 95.5 counts per A.

Is that correct?

I would appreciate if you validate my calculation and comment. Thanks.

0 Adam Sidelsky over 5 years ago in reply to Ananthkumar Selvaraj

This seems correct to me!

0 Ananthkumar Selvaraj over 5 years ago in reply to Adam Sidelsky

Thank you.

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